This invention relates to a protective coating composition. In one aspect the invention relates to a transparent abrasion resistant coating. In another aspect, the invention relates to a stable dispersion of colloidal silica and a silicone resin.
There is a need for transparent glazing materials which exhibit a greater resistance to shattering than glass. Synthetic organic polymers can be formed into transparent enclosures and these materials, such as polycarbonates and acrylics, are finding use in glazing for autos, buses and aircraft and as windows in public buildings. While these polymers are easily fabricated into the desired shape, and are less dense and have more resistance to breakage than glass, their abrasion resistance is relatively low. This lack of surface hardness and abrasion resistance has severely restricted the use of these transparent polymeric materials. Other uses of the polymeric materials, such as glazing decorative architectural panels and mirrors, are also limited because of this lack of abrasion resistance.
Scratch resistant coatings, such as silica-containing solutions and polysilicic acid fluorinated copolymer compositions, are available in the prior art. These materials have found only limited commercial use because they are difficult to apply, poor in humidity resistance, or expensive. The coating composition of the present invention is based on relatively inexpensive commercially available materials which are easily applied to substrates to provide an abrasion-resistant surface having good weathering characteristics.
Thus, it is an object of the present invention to provide a composition suitable as a protective coating for solid substrates. It is another object of the invention to provide an improved abrasion resistant coating for solid substrates, especially transparent substrates. It is a further object of the invention to provide dispersions from which the coatings of the invention can be applied. These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following description and appended claims.